This invention relates to an apparatus and a method for analyzing operation of an electronic circuit and, more particularly, for analyzing the operation of an electronic circuit using eye diagrams.
One way by which to determine the operational characteristics of an electronic circuit is by evaluating a stream of pulse coded signals, often referred to as a bit stream, which is produced by the electronic circuit. A bit stream is usually binary coded pulse signals represented by zeros and ones that may be electrical voltages or optical signals derived from the electrical voltages, created by the electronic circuit and monitored with an oscilloscope. The signal displayed on the oscilloscope that results from the bit streams is referred to as an “eye diagram”.
The eye diagram is made from thousands of voltage samples taken over a period of time that reveal the quality of the measured bit streams. In an eye diagram the high and low states of the signal appear as substantially horizontal traces across the oscilloscope screen. State transitions are not completely random. Each transition potentially occurs relative to a conversion clock signal. Thus, if a state transition occurs, it happens at a known time relative to the conversion clock signal. By triggering the oscilloscope with the conversion clock signal, the state transitions of the communication signal appear at substantially the same locations on the oscilloscope display. The resulting pattern is an open area, the eye, bounded on the top and bottom by the high and low state levels, respectively, and on each side by state transition traces. The state transitions on each side of the opening generally cross and form an “X” shape on each side of the eye. One component of each “X” shape corresponds to high-to-low transitions and the other component corresponds to low-to-high transitions. The distance between the high and low states, the slope of the state transition, overall size of the open area, and other similar measurements aid in characterizing the operation of the electronic circuit producing the eye pattern.
Typically the operational characteristics of an electronic circuit are evaluated with a myriad different inputs stimuli and a myriad of different output conditions. The result is that several hundred to several thousand eye diagrams may be generated to properly assess the operational characteristics of an electronic circuit.
A need exists, therefore, to provide a method and system to ascertain the operational characteristics of an electronic circuit employing eye diagrams.